feat: file upload + context compression + fix maxTokens

- Add file-service.ts: Azure Blob upload + PDF/Excel/image parsing
- Add truncate-messages.ts: context compression for long conversations
- Fix maxTokens: flash 500→2000, auto 2048→4096, pro 4096→8192
- Integrate truncateMessages in general-input and router nodes
- Add @azure/storage-blob, pdf-parse, xlsx dependencies

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

langgraph/package.json

@@ -19,6 +19,7 @@
     "@assistant-ui/react": "^0.8.0",
     "@assistant-ui/react-markdown": "^0.8.0",
     "@assistant-ui/react-syntax-highlighter": "^0.7.2",
+    "@azure/storage-blob": "^12.31.0",
     "@faker-js/faker": "^9.5.1",
     "@langchain/anthropic": "^0.3.18",
     "@langchain/core": "^0.3.45",
@@ -46,6 +47,7 @@
     "katex": "^0.16.21",
     "lucide-react": "^0.476.0",
     "next-themes": "^0.4.4",
+    "pdf-parse": "^2.4.5",
     "prettier": "^3.5.2",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
@@ -62,11 +64,13 @@
     "use-query-params": "^2.2.1",
     "use-stick-to-bottom": "^1.0.46",
     "uuid": "^11.0.5",
+    "xlsx": "^0.18.5",
     "zod": "^3.23.8"
   },
   "devDependencies": {
     "@eslint/js": "^9.19.0",
     "@types/node": "^22.13.5",
+    "@types/pdf-parse": "^1.1.5",
     "@types/react": "^19.0.8",
     "@types/react-dom": "^19.0.3",
     "@types/react-syntax-highlighter": "^15.5.13",